Pellicle frame and pellicle

ABSTRACT

The present invention is to provide a pellicle frame characterized by including a metal or alloy having a linear expansion coefficient of 10×10 −6  (1/K) or less and further a density of 4.6 g/cm 3  or less, and a pellicle characterized by including the pellicle frame as an element.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation application of application Ser. No.16/127,599, filed on Sep. 11, 2018, which claims the benefit under 35U.S.C. § 119(a) to Patent Application No. 2017-197004, filed in Japan onOct. 10, 2017, all of which are hereby expressly incorporated byreference into the present application.

TECHNICAL FIELD

The present invention relates to a pellicle for lithography used as adust guard when a semiconductor device such as large scale integration(LSI) and very large scale integration (VLSI), a printed board, a liquidcrystal display, or the like is produced.

BACKGROUND ART

When a semiconductor device such as LSI and VLSI, a liquid crystaldisplay, or the like is produced, a pattern is formed by irradiating asemiconductor wafer or an original plate for liquid crystal with light,and if dust adheres to a photomask or a reticle (hereinafter, simplyreferred to as a “photomask”), which is to be used at this time, theedge of the pattern becomes rough, and further there is a problem thatthe dimension, the quality, the appearance, or the like is impaired, forexample, the base becomes black and dirty.

For this reason, the pattern formation work is usually performed in aclean room, however, it is still difficult to keep the photomask clean.Therefore, exposure is performed after attaching a pellicle as a dustguard onto a surface of the photomask. In this case, foreign matters donot adhere directly onto a surface of the photomask but adhere onto thepellicle film, therefore, if the focal point is set on a pattern of thephotomask at the time of lithography, the foreign matters on thepellicle film become irrelevant to the transfer.

In general, a pellicle is obtained as follows: a good solvent for apellicle film is applied onto an upper end surface of a pellicle framemade of aluminum, stainless steel, polyethylene or the like, and thenair dried, and a transparent pellicle film made of nitrocellulose,cellulose acetate, a fluorine resin or the like, which well transmitslight, is bonded onto the upper end surface (see Patent Document 1), orthe pellicle film is bonded onto the upper end surface by an adhesiveagent of an acrylic resin, an epoxy resin or the like (see PatentDocuments 2 and 3). In addition, on a lower end of the pellicle frame, apressure-sensitive adhesive layer for the attachment onto a photomask,which is made of a polybutene resin, a polyvinyl acetate resin, anacrylic resin, a silicone resin or the like, and a release layer(separator) for the purpose of protecting the pressure-sensitiveadhesive layer, are arranged.

Further, in a case where such a pellicle is attached onto a surface of aphotomask, and a photoresist film formed on a semiconductor wafer or anoriginal plate for liquid crystal is exposed through the photomask,foreign matters such as dust adhere onto a surface of the pellicle anddo not adhere directly onto a surface of the photomask, therefore, theinfluence of the foreign matters such as dust can be avoided byperforming the irradiation with light for exposure so that the focalpoint is located on a pattern formed on the photomask.

By the way, in recent years, a semiconductor device and a liquid crystaldisplay have been increasingly highly integrated and miniaturizedactually. At present, a technique for forming a fine pattern of around32 nm on a photoresist film is being put into practical use. As long asthe pattern is around 32 nm, a space between a semiconductor wafer or anoriginal plate for liquid crystal and a projection lens is filled with aliquid such as ultrapure water, and by using an argon fluoride (ArF)excimer laser, the pattern can be realized by an immersion exposuretechnique for exposing a photoresist film, or an improved techniqueusing a conventional excimer laser, such as double exposure.

However, for a next-generation semiconductor device or liquid crystaldisplay, further miniaturized pattern formation of 10 nm or less isrequired, and it is no longer possible to form such a miniaturizedpattern of 10 nm or less by the improvement of a conventional exposuretechnique using an excimer laser.

Therefore, as a method for forming a pattern of 10 nm or less, anextreme ultra violet (EUV) exposure technique using EUV light having amain wavelength of 13.5 nm is promising. In a case where a fine patternof 10 nm or less is formed on a photoresist film by using the EUVexposure technique, it is required to solve technical problems such as:what type of light source is used, what type of photoresist is used, andwhat type of pellicle is used. Among these technical problems, as to anew light source and a new photoresist material, the development hasprogressed and various proposals have been made.

With respect to a pellicle that affect the yield of a semiconductordevice or a liquid crystal display, for example, in Patent Document 3, asilicon film having a thickness of 0.1 to 2.0 μm that is transparent anddoes not cause optical distortion is described as a pellicle film to beused for EUV lithography, however, in order to apply in practice,unresolved problems still remain and are a major obstacle to putting theEUV exposure technique into practical use in actuality.

Conventionally, as the material for a pellicle frame constituting apellicle, in the exposure using an i-line (having a wavelength of 365nm), a krypton fluoride (KrF) excimer laser light (having a wavelengthof 248 nm), an argon fluoride (ArF) excimer laser light (having awavelength of 193 nm), usually aluminum, stainless steel, polyethyleneor the like is used, which are selected by taking only the rigidity andthe processability into consideration.

On the other hand, as the material for a photomask, quartz glass isusually used in many cases. Further, as the pellicle film, if it is foran i-line, for KrF, or for ArF, nitrocellulose, cellulose acetate, afluorine resin or the like is used, and if it is for EUV, a transparentfilm corresponding to a light source, such as silicon, is used.

However, in a case where a fine pattern of 10 nm or less is formed on aphotoresist film by using the EUV exposure technique, when aconventional pellicle is used, wrinkles may be formed in the pelliclefilm, or the pellicle film may come off from a frame for a pellicle ormay be torn or broken.

In Patent Document 4, it has been found that the wrinkle generation andbreakage of the pellicle film are caused by expansion and contraction,and distortion of a pellicle frame, which can be caused by a temperaturerise due to the light energy at the time of exposure, and it has beenproposed that a material having a linear expansion coefficient of10×10⁻⁶ (1/K) or less is used for the frame.

However, a material such as Si, SiO₂, SiC or SiN, which has a lowthermal expansion coefficient, is brittle, therefore, there is a problemof difficulty in the processing. In particular, for an EUV pellicle,since the pellicle arrangement space in an EUV exposure device is small,the height of the pellicle is required to be 2.5 mm or less.

Further, in general, on a side face of a pellicle frame of a pellicle, ajig hole used for handling or peeling off the pellicle from a photomask,and a ventilation part for reducing the pressure difference between theinside and outside of the pellicle are provided. In addition, in EUVlithography, in order to make the inside of an exposure device vacuum, apellicle for EUV is required to withstand the pressure changes from theatmospheric pressure to the vacuum, and a ventilation part of the EUVpellicle is required to have a large area.

For example, the thickness of a pellicle frame for an EUV pellicle issmaller than 2.5 mm, however, in a case where a hole having a diameterof 1 mm is provided on a side face of a pellicle frame made of amaterial such as Si, SiO₂, SiC or SiN, the thickness in the vicinity ofthe hole of the pellicle frame may become small, and there is a highpossibility that the pellicle frame is broken during the processing of ahole or during the peeling of a pellicle. If it is required to increasethe area of the ventilation part, the possibility of breakage is furtherincreased.

Therefore, it can also be considered that a metal such as invar is usedas a material having a low thermal expansion coefficient. A metal and analloy are easy to process, and are not broken even if a hole is providedon a side face of a pellicle frame.

By the way, the width of a pellicle frame is preferably as small aspossible in order to widen the exposure area, and the width has beenaround 2 mm from the past. However, it has been found that in a case ofan EUV pellicle, the width of a pellicle frame is limited by a pelliclefilm, and it is required to set the width as large as around 3 to 4 mm.

Further, in recent years, for the purpose of improving the throughput ofEUV production, faster movement of a mask stage is required, and thetotal weight of a pellicle is required to be 15 g or less.

However, in a case where the width is changed from 2 mm to 4 mm, thevolume of the pellicle frame is around twice, and even in a case wherethe width is 3 mm, the volume is around 1.5 times. Subsequently, it wasfound that the weight of a pellicle frame prepared by invar becomesextremely high.

CITATION LIST

Patent Document 1: JP-A S58-219023

Patent Document 2: U.S. Pat. No. 4,861,402

Patent Document 3: JP-B S63-27707

Patent Document 4: JP-A 2016-200616

SUMMARY OF THE INVENTION

The present invention has been made in view of such circumstances, andan object of the present invention to provide: a pellicle frame withwhich in a case where a fine pattern of 10 nm or less is formed on aphotoresist film by using an EUV exposure technique, a situation inwhich wrinkles may be formed in a pellicle film, or the pellicle filmmay come off from a pellicle frame or may be torn or broken can beeffectively prevented, and further the weight is low and the risk ofbreakage is low; and a pellicle using the pellicle frame.

The present inventors have found that by using a metal or alloy having alinear expansion coefficient of 10×10⁻⁶ (1/K) or less and further adensity of 4.6 g/cm³ or less for a pellicle frame in a frame shapehaving an upper end face on which a pellicle film is to be arranged anda lower end face to face a photomask, the pellicle frame is mostsuitable for the latest EUV exposure technique because wrinkles orbreakage is not generated in a pellicle film and the weight is low, andthus have completed the present invention.

Therefore, the present invention provides the following pellicle frameand pellicle.

1. A pellicle frame, including: a metal or alloy having a linearexpansion coefficient of 10×10⁻⁶ (1/K) or less and a density of 4.6g/cm³ or less.

2. The pellicle frame according to 1, wherein the metal or alloy istitanium or a titanium alloy.

3. The pellicle frame according to 1, wherein the pellicle frame has athickness of less than 2.5 mm.

4. The pellicle frame according to 1, wherein one or a plurality ofholes is provided on a side face.

5. A pellicle, including: the pellicle frame according to 1 as anelement.

Advantageous Effects of the Invention

According to the pellicle frame and pellicle of the present invention,even if the temperature of a pellicle frame is increased by the lightenergy due to exposure, expansion and contraction, and distortion of thepellicle frame can be suppressed to be lower, and wrinkles or breakageis not generated in a pellicle film. In addition, since the pellicleframe and pellicle according to the present invention is excellent inthe processability, the improvement of the yield is expected, and thearea of a ventilation part can be set larger, and further, the pellicleframe and pellicle have little risk of breakage during pellicle peelingor the like, and are lightweight, therefore, the pellicle frame andpellicle can be applied to the latest EUV exposure technique.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are schematic views (Example) showing one embodiment of apellicle frame according to the present invention, FIG. 1A is a view asviewed from a lower end face side, FIG. 1B is a view as viewed from anouter face side of the long side, and FIG. 1C is a view as viewed froman outer face side of the short side; and

FIGS. 2A to 2C are schematic views showing another embodiment of thepellicle to frame according to the present invention, FIG. 2A is a viewas viewed from a lower end face side, FIG. 2B is a view as viewed froman outer face side of the long side, and FIG. 2C is a view as viewedfrom an outer face side of the short side.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The pellicle frame according to the present invention usually has anupper end face on which a pellicle film is to be arranged and a lowerend face to face a photomask. Further, the shape of the pellicle frameis a frame shape corresponding to the shape of a photomask onto which apellicle is to be attached. In general, the shape of the pellicle frameis a quadrilateral (rectangular or square) frame shape.

The pellicle frame has an upper end face on which a pellicle film is tobe arranged and a lower end face to face a photomask when the pellicleframe is attached onto a photomask. In general, on the upper end face, apellicle film is arranged with an adhesive agent or the liketherebetween, and on the lower end face, a pressure-sensitive adhesiveor the like for attaching a pellicle onto a photomask is provided, butcases of the present invention are not limited to the above.

The size of a pellicle frame is not particularly limited, however, sincethe height of a pellicle for EUV is limited to 2.5 mm or less, thethickness of a pellicle frame for EUV is smaller than the height and isless than 2.5 mm. Actually, the thickness of the pellicle frame ispreferably 2.0 mm or less and more preferably 1.6 mm or less inconsideration of the thickness of a pellicle film, a maskpressure-sensitive adhesive and the like.

Further, in order to sufficiently exhibit a function as a pellicle, thepellicle frame is required to have a height of 1.5 mm or more. In thisregard, the thickness of a pellicle frame for EUV is preferably 1.0 mmor more in consideration of the thickness of a pellicle film, a maskpressure-sensitive adhesive and the like.

In addition, usually, on a side face of a pellicle frame, a jig holeused for handling or peeling off the pellicle from a photomask, and aventilation part for reducing the pressure difference between the insideand outside of the pellicle are provided. Further, in EUV lithography,in order to make the inside of an exposure device vacuum, a pellicle forEUV is required to withstand the pressure changes from the atmosphericpressure to the vacuum, and a ventilation part of the EUV pelliclepreferably has an area as large as possible.

Therefore, a hole is preferably provided on a side face of the pellicleframe, and the size of a jig hole or vent hole is 0.5 to 1.0 mm inlength (diameter in a case of a circle) in a thickness direction of theframe. The shape of the hole is not limited, and may be a circle or arectangle. In addition, usually, the jig hole is a hole that does notpenetrate from an outer side face to an inner side face, and the venthole is a hole that penetrates from an outer side face to an inner sideface.

In a case where a hole is provided on a side face of a pellicle frame, amargin of at least 0.2 mm is required around the processed hole in orderto keep the restrictions on processing and the strength of the frame. Ifa jig hole or vent hole having a length size of 1.0 mm or more in athickness direction of the frame is provided, the thickness of the frameis preferably 1.4 mm or more.

In general, as to the size of a pellicle frame for EUV, the outer lengthof the long side is 145 to 152 mm, the outer length of the short side is113 to 120 mm, the thickness is 1.0 to 2.0 mm, and the width is 3.0 to4.0 mm. Further, the volume of the pellicle frame is preferably 3.2 cm³or less, and more preferably 2.6 cm³ or less.

In the present invention, as the material for a pellicle frame, a metalor alloy having a linear expansion coefficient of 10×10⁻⁶ (1/K) or lessand further a density of 5 g/cm³ or less is used.

In the present invention, by using a metal or an alloy as the materialfor a pellicle frame, a hole can be provided on a side face even with amargin of 0.2 mm. For example, a hole having a diameter of 1.0 mm can beprovided on a side face of a pellicle frame having a thickness of 1.5mm. At this time, the margin on each of the above and below of the holeis 0.25 mm.

In addition, in a case of forming a hole in a pellicle frame made of abrittle material such as a silicon single crystal, a margin of at least0.5 mm is required around the hole. Therefore, on a side face of apellicle frame having a thickness of 1.5 mm, only a hole having adiameter of up to 0.5 mm can be formed. In this case, there is a fearthat the size of a ventilation part as an EUV pellicle becomesinsufficient, and further in order to reliably hold or peel off with ajig hole having a diameter of 0.5 mm, it is required to increase thenumber of holes, and the yield is also lowered. Moreover, even if themargin is 0.5 mm, there is a high possibility of breakage when a largeforce is applied as during peeling.

In the present invention, the material for a pellicle frame has a linearexpansion coefficient of 10×10⁻⁶ (1/K) or less, and if the linearexpansion coefficient is within this range, expansion and contraction,and distortion of the pellicle frame, which can be caused by atemperature rise due to the light energy at the time of exposure, can besuppressed sufficiently to be smaller, so that the generation ofwrinkles or breakage on a pellicle film can be prevented.

In addition, in the present invention, the density of a metal or alloythat is a material for a pellicle frame is 4.6 g/cm³ or less. If thedensity is within this range, the weight can be reduced to 15 g or lessin a pellicle frame having a volume of 3.2 cm³ or less. However, in acase where the volume of a pellicle frame exceeds 2.6 cm³, it isrequired to reduce the weight of the pellicle film or maskpressure-sensitive adhesive other than the pellicle frame to 3 g orless. Therefore, the volume of a pellicle frame is preferably 2.6 cm³ orless, and the density is also more preferably 4.5 g/cm³ or less.

As such a metal or alloy, titanium, or a titanium alloy such as aTi—V—Al alloy, and a Ti—V—Cr—Sn—Al alloy can be mentioned, and can bepreferably used.

In the pellicle according to the present invention, a pellicle film isarranged on an upper end face of the above pellicle frame with apressure-sensitive adhesive or an adhesive agent therebetween. Thematerial for the pressure-sensitive adhesive or the adhesive agent isnot limited, and a known material can be used. For example, a goodsolvent for a pellicle film is applied, and then may be air dried andbonded, or an adhesive agent or pressure-sensitive adhesive of anacrylic resin, a silicone resin, an epoxy resin or the like may be used.

In addition, there is no restriction on the material for a pelliclefilm, and as the material, a material having a high transmittance at awavelength of an exposure light source and a high light resistance ispreferred. For example, for an excimer laser, an amorphous fluoropolymeror the like may be used. Examples of the amorphous fluoropolymer includeCYTOP [trade name, manufactured by ASAHI GLASS CO., LTD.], and Teflon(registered trademark) AF [trade name, manufactured by E. I. du Pont deNemours and Company].

In addition, an ultrathin silicon film that is constituted of amonocrystalline silicon, a polycrystalline silicon, or an amorphoussilicon, or a carbon film is used for EUV exposure. The pellicle filmmay be provided with a protective film of SiC, SiO₂, Si₃N₄, SiON, Y₂O₃,YN, Mo, Ru, Rh or the like.

Further, on a lower end face of a pellicle frame, a pressure-sensitiveadhesive for the attachment onto a photomask is formed. As the maskpressure-sensitive adhesive, a known mask pressure-sensitive adhesivecan be used, and a pressure-sensitive adhesive made of a polybuteneresin, a polyvinyl acetate resin, apoly(styrene-ethylene-butadiene-styrene) (SEBS) resin, an acrylic resin,a silicone resin or the like can be used. In particular, apressure-sensitive adhesive made of an acrylic resin, or a siliconeresin is preferred.

The application of a pellicle film adhesive agent and a maskpressure-sensitive adhesive can be performed by using a coatingapplicator or the like, for example, by dipping, spraying, brushing, ora dispenser, and the application using a coating applicator by adispenser is preferred from the viewpoint of the stability, theworkability, the yield, or the like.

In addition, the pressure-sensitive adhesive or the adhesive agent isgenerally formed so as to have a width equal to or smaller than thewidth of a pellicle frame over the entire circumferential direction ofan end face of the pellicle frame.

Further, in a case where the viscosity of each of a pellicle filmadhesive agent and a mask pressure-sensitive adhesive is high and theapplication using a coating applicator is difficult, into the pelliclefilm adhesive agent and the mask pressure-sensitive adhesive, anaromatic solvent such as toluene, and xylene; an aliphatic solvent suchas hexane, octane, isooctane, and isoparaffin; a ketone-based solventsuch as methyl ethyl ketone, and methyl isobutyl ketone; an ester-basedsolvent such as ethyl acetate, and butyl acetate; an ether-based solventsuch as diisopropyl ether, and 1,4-dioxane; or a mixed solvent thereofmay be added as needed.

Onto a lower end face of a mask pressure-sensitive adhesive, a releaselayer (separator) for protecting the pressure-sensitive adhesive may beattached. There is no particular restriction on the material for therelease layer, and for example, polyethylene terephthalate (PET),polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinylether copolymer (PFA), polyethylene (PE), polycarbonate (PC), polyvinylchloride (PVC), polypropylene (PP), or the like can be used. Further, asneeded, a release agent such as a silicone-based release agent or afluorine-based release agent may be applied onto a surface of therelease layer.

In a case where a hole penetrating from an outer side face to an innerside face is provided in a pellicle frame, a filter for dust removal maybe arranged for the purpose of particle removal. The filter may bearranged inside the hole or may be arranged on a side face so as tocover the opening part of the hole.

In addition, in a pellicle frame for EUV, the total area of the openingparts of vent holes is preferably 5 mm² or more, and more preferably 10mm² or more. For example, the vent hole may be penetrated from an outerside face toward an inner side face so as to form a recess on a lowerend face of the pellicle frame.

Herein, FIGS. 1A to 1C, and 2A to 2C show an example of a pellicle 1including the pellicle frame 2 according to the present invention as anelement. A pellicle film 3 is bonded and stretched onto an upper endface of the pellicle frame 2 by an adhesive agent 5. Further, on a lowerend face of the pellicle frame 2, a pressure-sensitive adhesive 4 forthe attachment onto a photomask (not shown) is provided. In addition, inthe drawing, the reference sign 6 shows a vent hole, and in a pellicleframe in FIGS. 2A to 2C, a vent hole is formed so as to form a recess 6on a lower end face of the pellicle frame unlike in the case of FIGS. 1Ato 1C. In addition, usually, the reference sign 7 shows a jig holeformed for peeling off a pellicle from a photomask by using a jig.

EXAMPLES

Hereinafter, the present invention is specifically described withreference to Examples and Comparative Examples, however, the presentinvention is not limited to the following Examples.

Example 1

A pellicle frame (with an outer size of 150 mm×118 mm×1.5 mm, and aframe width of 3.0 mm) made of titanium (having a linear expansioncoefficient of 8.4×10⁻⁶ (1/K), and a density of 4.5 g/cm³) was prepared.

On an outer side face of the long side of the pellicle frame, two jigholes each having a diameter of 1 mm and a depth of 1.2 mm were providedat two places each with a distance of 52 mm away from the center of theside in the corner direction. In addition, six through holes wereprovided at six places with a distance of 10 mm, 30 mm, and 65 mm,respectively away from the center of the long side in the cornerdirection, and four through holes were provided at four places with adistance of 10 mm, and 30 mm, respectively away from the center of theshort side in the corner direction.

This pellicle frame was washed with a neutral detergent and pure water,and dried, and then a silicone pressure-sensitive adhesive (X-40-3264manufactured by Shin-Etsu Chemical Co., Ltd.) was applied over theentire circumference of the upper and lower end faces of the frame.

After that, the pellicle frame was heated at 90° C. for 12 hours to curethe pressure-sensitive adhesive on the upper and lower end faces.Subsequently, an ultrathin silicon film as a pellicle film was pressbonded to the pressure-sensitive adhesive formed on the upper end faceof the frame, and a pellicle was completed.

Herein, the volume of the pellicle frame was around 2.4 cm³, and thetotal weight of the pellicle film and the pressure-sensitive adhesivewas around 3.1 g.

Example 2

As the material for a pellicle frame, a Ti-Al6-V4 titanium alloy (havinga linear expansion coefficient of 8.8×10⁻⁶ (1/K), and a density of 4.4g/cm³), which is an alloy of titanium, aluminum and vanadium, was used.Except for the above-described material for a pellicle frame, a pelliclewas prepared in a similar manner as in Example 1.

Comparative Example 1

As the material for a pellicle frame, a quartz glass (SiO₂) (having alinear expansion coefficient of 0.5×10⁻⁶ (1/K), and a density of 2.2g/cm³) was used. Except for the above-described material for a pellicleframe, a pellicle was prepared in a similar manner as in Example 1.

In this case, when jig holes or through holes were provided in thepellicle frame, 7 out of 10 were broken. Further, when a pellicle wastried to be peeled off from the quartz substrate by using a peeling jigafter the heat cycle test described later, the jig hole was broken.

Comparative Example 2

As the material for a pellicle frame, a silicon nitride (Si₃N₄) (havinga linear expansion coefficient of 2.8×10⁻⁶ (1/K), and a density of 3.2g/cm³) was used. Except for the above-described material for a pellicleframe, a pellicle was prepared in a similar manner as in Example 1.

In this case, when jig holes or through holes were provided in thepellicle frame, 9 out of 10 were broken. Further, when a pellicle wastried to be peeled off from the quartz substrate by using a peeling jigafter the heat cycle test described later, the jig hole was broken.

Comparative Example 3

As the material for a pellicle frame, invar (Fe—Ni36) (having a linearexpansion coefficient of 1.5×10⁻⁶ (1/K), and a density of 8.1 g/cm³) wasused. Except for the above-described material for a pellicle frame, apellicle was prepared in a similar manner as in Example 1.

Comparative Example 4

As the material for a pellicle frame, aluminum (Al) (having a linearexpansion coefficient of 23×10⁻⁶ (1/K), and a density of 2.7 g/cm³) wasused. Except for the above-described material for a pellicle frame, apellicle was prepared in a similar manner as in Example 1.

The pellicles prepared in Examples 1 and 2 and Comparative Examples 1 to4 were subjected to a heat cycle test shown below. In Table 1, theprocessability of each material as a pellicle frame, the results of aheat cycle test, the pellicle weight, and the overall evaluation resultsof each pellicle are shown.

[Heat Cycle Test]

A cycle in which a pellicle attached onto a quartz substrate was heatedat 200° C. in an oven and left to stand for 24 hours, and then was leftto stand further for 24 hours at room temperature was repeated fivetimes. After that, the state of the pellicle was visually confirmed.

TABLE 1 Linear expansion Density Heat Pellicle weight Overall Materialcoefficient [1/K] [g/cm³] Processability cycle test [g] evaluationExample 1 Ti 8.4 × 10⁻⁶ 4.5 Favorable (no breakage) Favorable 13.9 ◯Example 2 Ti—Al—V 8.8 × 10⁻⁶ 4.4 Favorable (no breakage) Favorable 13.7◯ Comparative SiO₂ 0.5 × 10⁻⁶ 2.2 7 out of 10 were broken Favorable 8.4X Example 1 Comparative Si₃N₄ 2.8 × 10⁻⁶ 3.2 9 out of 10 were brokenFavorable 10.8 X Example 2 Comparative Fe—Ni 1.5 × 10⁻⁶ 8.1 Favorable(no breakage) Favorable 22.5 X Example 3 Comparative Al  23 × 10⁻⁶ 2.7Favorable (no breakage) Poor (pellicle 9.6 X Example 4 film was broken)

According to the results in Table 1, the pellicles of Examples 1 and 2had favorable heat cycle test results and also had favorableprocessability, and the pellicle weight was also able to be suppressedto 15 g or less.

On the other hand, the pellicles of Comparative Examples 1 and 2 had aproblem in the processability, and had difficulty of forming a hole in aside face part.

The pellicle of Comparative Example 3 had favorable heat cycle testresults and also had favorable processability, however, the pellicleweight exceeded 15 g, therefore, the pellicle cannot be applied to EUVlithography.

The pellicle frame of Comparative Example 4 had large expansion andcontraction of a frame for a pellicle by a heat cycle test, and thepellicle film was broken.

Japanese Patent Application No. 2017-197004 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

The invention claimed is:
 1. An exposure method comprising performing anextreme ultra violet (EUV) exposure using EUV light by using a pellicle,wherein the pellicle comprises a pellicle frame as an element thepellicle frame comprises a metal or alloy having a linear expansioncoefficient of 10×10⁻⁶ (1/K) or less and a density of 4.6 g/cm³ or less.2. The exposure method of claim 1, wherein the eta or alloy in thepellicle frame is titanium or a titanium alloy.
 3. The exposure methodof claim 1, wherein one or a plurality of holes is provided on a sideface of the pellicle frame.
 4. The exposure method of claim 3, whereinthe size of the holes is 0.5 to 1.0 mm in length in a thicknessdirection of the frame.
 5. The exposure method of claim 1, wherein thepellicle frame has a width of from 3.0 to 4.0 mm.
 6. The exposure methodof claim 1, wherein the pellicle frame has an outer length of a longside of from 145 to 152 mm, an outer length of a short side of from 113to 120 mm, a thickness of from 1.0 to 2.0 mm, and the width of from 3.0to 4.0 mm.
 7. The exposure method of claim 1, wherein the pellicle framehas a volume of 3.2 cm³ or less.
 8. The exposure method of claim 1,wherein vent holes are formed in the pellicle frame and the total areaof the opening parts of the vent holes is 5 mm² or more.
 9. Amanufacturing method of a semiconductor device, comprising a step offorming a pattern on a semiconductor wafer by using the EUV exposuremethod of claim
 1. 10. A manufacturing method of a liquid crystaldisplay, comprising a step of forming a pattern on an original plate forliquid crystal by using the EUV exposure method of claim
 1. 11. Anexposure method comprising performing an extreme ultra violet (EUV)exposure using EUV light by using a pellicle, wherein the pelliclecomprises a pellicle frame as an element and the pellicle framecomprises titanium or a titanium alloy.
 12. A pellicle, comprising: apellicle frame comprising a metal or alloy having a linear expansioncoefficient of 10×10⁻⁶ (1/K) or less and a density of 4.6 g/cm³ or less,and a pellicle film having a property applicable to extreme ultra violet(EUV) lithography.
 13. The pellicle of claim wherein one or a. pluralityof holes is provided on a side face of the pellicle frame.
 14. Thepellicle of claim 13, wherein the size of the holes is 0.5 to 1.0 mm inlength in a thickness direction of the pellicle frame.
 15. The pellicleof claim wherein the pellicle frame has a width of from 3.0 to 4.0 mm.16. The pellicle of claim 12, wherein the pellicle frame has an outerlength of a long side of from 145 to 152 mm, an outer length of a shortside of from 113 to 120 mm, a thickness of from 1.0 to 2.0 mm, and thewidth of from 3.0 to 4.0 mm.
 17. The pellicle: claim 12, wherein thepellicle frame has a volume of 3.2 cm³ or less.
 18. The pellicle ofclaim 12, wherein vent holes are formed in the pellicle frame and thetotal area of the opening parts of the vent holes is 5 mm² or more. 19.A photomask attaching a pellicle, wherein the pellicle of claim 12 isattached onto a surface of a photomask having a property applicable toEUV lithography.
 20. A pellicle, comprising: a pellicle frame comprisingtitanium or a titanium alloy, and a pellicle having a propertyapplicable to extreme ultra violet (EUV) lithography.
 21. The pellicleof claim 20, wherein one or a plurality of holes is provided on a sideface of the pellicle frame.
 22. The pellicle of claim 21, wherein thesize of the holes is 0.5 to 1.0 mm in length in a thickness direction ofthe pellicle frame.
 23. The pellicle of claim 20, wherein pellicle framehas a width of from 3.0 to 4.0 mm.
 24. The pellicle of claim 20, whereinthe pellicle frame has an outer length of a long side of from 145 to 152mm, an outer length of a short side of from 113 to 120 mm, a thicknessof from 1.0 to 2.0 mm, and the width of from 3.0 to 4.0 mm.
 25. Thepellicle of claim 20, wherein the pellicle frame has a volume of 3.2 cm³or less.
 26. The pellicle of claim 20, wherein vent holes are formed inthe pellicle frame and the total area of the opening parts of the ventholes is 5 mm² or more.
 27. A photomask attaching a pellicle, whereinthe pellicle of claim 20 is attached onto a surface of a photomaskhaving a property applicable to EUV lithography.